set term eps
set output "optimization3.eps"
set xrange [-1:1]
set xlabel "x" font "Arial,20"
set ylabel "y" font "Arial,20"
set xtics ("0.1" 0.1, "0" 0, "-0.1618" -0.1618, "-1" -1, "1" 1)
set label "a" at 0.1, 0.7
set label "b" at 0, 0.7
set label "c" at -0.1618, 0.7
plot x*x+x+1 with line lw 3 title "f(x)=x^2+x+1"

#set arrow from -1+2.0/19*5, 1.2 to -1+2.0/19*5, 0.8
